Magnetic recording media hitherto used widely, including videotapes, audio tapes and magnetic disks, are materials which each have a non-magnetic support coated with a magnetic layer containing a particulate ferromagnetic substance, such as particulate ferromagnetic iron oxide, cobalt-modified ferromagnetic iron oxide, CrO2 or ferromagnetic alloy, dispersed in a binder.
Recent years have seen trends for the track width to be narrowed and for the recording wavelength to be shorten with increases in recording density. Under these circumstances, reproduction with a high-sensitivity magnetoresistance head (hereinafter referred to as “an MR head”) has been proposed and put into practice.
Recording media used in recording with an MR head are required to have characteristics different from those of recording media hitherto used in recording with an inductive head. In the first place, recording with an MR head requires that recording media reduced in residual magnetization be used. This is because saturation of the MR head occurs when recording media have thick magnetic layers, and their residual magnetization becomes too great. In the second place, the recording media are required to use particulate magnetic substances and have smooth magnetic surfaces for the purpose of reducing medium noises because an MR head has high sensitivity.
In an attempt to address these requirements, head saturation is prevented by reducing the magnetic layer thickness to the range of 0.01 to 0.3 μm and adjusting the residual magnetization to the range of 5 to 50 A·m2/kg, and modulation noises are reduced by defining the intensities of roughness components at specific spatial frequencies (See JP-A-2001-256633).
In another attempt to prevent head saturation and reduce noises at the same time, the magnetic layer is formed with a thickness less than the shortest bit length and the volume filling degree of ferromagnetic powders in a magnetic layer, to which nonmagnetic powders are also added, is adjusted so as to fall within the range of 15 to 35% (See JP-A-2002-92846).
Although the noise reduction has been underway as mentioned above, it has resulted in a discovery that there are problems with head abrasion and durability. An MR head has a configuration that an MR element is imbedded in a low hardness shield layer which is arranged between substrates made of high hardness materials. Therefore, the shield layer containing the MR element is selectively worn away, and a level difference develops between the substrates and the shield layer, thereby increasing a spacing loss. As a result, there occurs a problem that the output is lowered.
In order to minimize those undesirable influences, improvements in electromagnetic conversion characteristics have been attempted by rendering the magnetic layer surface smooth and reducing the spacing loss. However, such a measure yields a detriment that the magnetic layer surface is susceptible to abrasion marks.